JP2006244500A - Reference voltage generation part and method of generating reference voltage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reference voltage generation part and to provide a method of generating a reference voltage. <P>SOLUTION: This reference voltage generation part generates a reference voltage which changes with temperature. For example, the reference voltage generation part may generate a reference voltage that decreases as temperature increase. The reference voltage generation part is configured to selectively adjust a temperature coefficient of the reference voltage at a selected temperature value to generate the reference voltage having the same voltage value regardless of the temperature coefficient. Thereby, the reference voltage generation part can improve the reliability of a liquid crystal display device at high temperature, can generate the same reference voltage at stable ordinary temperature even if the temperature coefficient is different and can supply a stable voltage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reference voltage generator.

  The reference voltage generator is used in many devices. For example, a reference voltage generator used in a liquid crystal display device generates a driving voltage used for a gate driver and a source driver of the liquid crystal display device. The reference voltage generator can generate a desired reference voltage according to the temperature and prevent an adverse effect due to the temperature.

  FIG. 1 is a circuit diagram illustrating a general reference voltage generator that generates various reference voltages according to temperature.

  Referring to FIG. 1, the reference voltage generator includes a temperature proportional unit 52 having a property that the voltage consumed by the current mirror circuit 51 and the resistor R2 is proportional to temperature (Proportional To Absolute Temperature; PTAT), And a temperature inversely proportional part 53 having a property inversely proportional to (Complementary To Absolute Temperature; CTAT).

The current mirror circuit 51 includes a first PMOS transistor (TP1), a first NMOS transistor (TN1) connected in series between a power supply voltage (V _DD ) and a ground voltage (V _SS ), Resistance (R1). The current mirror circuit 51 includes a second PMOS transistor (TP2) and a second NMOS transistor (TN2) connected in series between the power supply voltage (V _DD ) and the ground voltage (V _SS ). . The gate of the first PMOS transistor (TP1) is connected to the gate of the second PMOS transistor (TP2). Similarly, the gate of the first NMOS transistor (TN1) is connected to the gate of the second NMOS transistor (TN2). The drain of the first PMOS transistor (TP1) is connected to the gate of the first PMOS transistor (TP1), and the drain of the second NMOS transistor (TN2) is connected to the gate of the second NMOS transistor (TN2). Is done. The ratio of the region of the first NMOS transistor (TN1) to the region of the second NMOS transistor (TN2) is P.

  The current mirror circuit 51 includes a third PMOS transistor (TP3) connected in parallel with the first and second PMOS transistors (TP1, TP2). The gate of the third PMOS transistor (TP3) is connected to the gate of the second PMOS transistor (TP2).

The temperature proportional unit 52 and the temperature inverse proportional unit 53 are connected in series between the power supply voltage (V _DD ) and the ground voltage (V _SS ) together with the third PMOS transistor (TP3). The temperature proportional unit 52 includes a variable resistor (R2). The temperature inversely proportional portion 53 includes a bipolar junction transistor (TB). The base of the transistor (TB) is connected to the collector.

The current (I _x ) generated by the operation of the current mirror circuit 51 is mirrored, and the current (I _y ) flows through the temperature proportional unit 52 and the temperature inverse proportional unit 53. The reference voltage (Vref) of the reference voltage generating unit is generated by the current flowing through the temperature proportional unit 52 and the temperature inverse proportional unit 53. The voltage (V _x ) applied to both ends of the resistance (R2) of the temperature proportional unit 52 is IyR2, where I _y = mI _x . Here, m represents the size ratio of the third PMOS transistor (TP3) with respect to the size of the second PMOS transistor (TP2). Thereon, Ix = VT (ζ) ( 1 / R1) lnP, this time, the zeta, a step constant having a value between -1 to 2, _{V T} is the thermal voltage shown in kT / q Where T is the temperature, k is the Boltzmann constant, and q is the amount of charge. In the temperature inversely proportional unit 53, VBE generates a voltage such as V _T ln (Iy / Is). Here, Is represents a saturation current depending on the size of the transistor (TB). Therefore, the reference voltage (Vref) is Vx + VBE.

  FIG. 2 is a graph illustrating reference voltages according to temperatures having different temperature coefficients in the reference voltage generation unit illustrated in FIG.

  Referring to FIG. 2, the temperature coefficient is changed at a constant temperature (25 ° C.), and the value of the output reference voltage (Vref) cannot be fixed to one value.

  The technical problem of the present invention is to provide a reference voltage generator that can implement various temperature coefficients whose reference voltage is inversely proportional to temperature, and can generate the same reference voltage at a constant temperature even if the temperature coefficients are different. .

  Another technical problem of the present invention is to provide a reference voltage generation method of the reference voltage generator as described above.

  Still another technical problem of the present invention is to provide a display driver circuit including the reference voltage generator as described above.

  In order to achieve the above technical problem, the reference voltage generating unit according to the present invention includes a reference voltage generating circuit that generates a reference voltage that is variable according to temperature, and the reference voltage generating circuit selects a temperature coefficient of the reference voltage. The reference voltage has the same voltage level regardless of the temperature coefficient.

  In order to achieve the technical problem described above, a reference voltage generator according to the present invention includes a first voltage generator that generates a first voltage, a second voltage generator that generates a second voltage, A voltage subtracting unit that generates a reference voltage obtained by subtracting the first voltage from the voltage of 2.

  In order to achieve the other technical problems described above, the reference voltage generation method according to the present invention includes generating a reference voltage having the same voltage value regardless of the temperature coefficient of the reference voltage at the selected temperature value.

  In order to achieve the above-described further technical problem, a display driver circuit according to the present invention includes a reference voltage generator, and the reference voltage generator has a temperature coefficient of the reference voltage at a selected temperature even when the temperature changes. Regardless of whether a reference voltage having a constant voltage value is generated, at least one gate driver voltage is generated in response to the reference voltage and a source driver voltage is generated, and a display panel in response to the source driver voltage A source driver for generating a source driving signal and a gate driver for generating a gate driving signal in the display panel in response to a gate driver voltage.

  According to the present invention, a reference voltage generation unit that generates a reference voltage that is inversely proportional to temperature is provided, so that a stable voltage can be supplied to the gate driver of the liquid crystal display device even at a high temperature. Can improve the reliability. In addition, a voltage having various temperature coefficients inversely proportional to the temperature can be generated using the reference voltage generation unit, and the same reference voltage can be generated at a constant room temperature even if the temperature coefficient is different, so that a stable voltage supply effect can be obtained. Obtainable.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 3 is a circuit diagram illustrating a reference voltage generator according to an embodiment of the present invention.

  Referring to FIG. 3, the reference voltage generation unit includes a current mirror circuit 86, a temperature proportional unit 84, and a voltage generation unit 85 independent of temperature. The temperature proportional unit 84 and the temperature independent voltage generator 85 generate a first voltage (V1) and a second voltage (V2) by the current applied from the current mirror circuit 86. The buffer amplifier 82 passes the first voltage (V1), and the voltage subtractor 83 generates the reference voltage (Vref) using the buffered first voltage (V1) and the second voltage (V2). To do.

  The temperature proportional unit 84 has a constant temperature coefficient, for example, + 0.2% / ° C., and generates a first voltage (V1) that is proportional to a change in temperature. Conversely, the temperature-independent voltage generator 85 generates a constant second voltage (V2) regardless of the temperature change. The temperature proportional unit 84 and the temperature independent voltage generation unit 85 are described later in detail together with the current mirror circuit 86.

  The buffer amplifier 82 includes a first operational amplifier (A1) in which an output terminal is connected to an inverting input terminal and a first voltage (V1) is applied to a non-inverting input terminal. The buffer amplifier 82 prevents unnecessary current from flowing from the temperature proportional unit 84. The voltage subtracter 83 includes a second operational amplifier (A2). The second voltage (V2) is applied to the non-inverting input terminal of the second operational amplifier (A2), and the buffered first voltage (V1) through the first resistor (R10) is used as the inverting input terminal. Is applied. A second resistor (R20) is connected between the inverting input terminal and the output terminal of the second operational amplifier (A2). The second operational amplifier (A2) is a differential amplifier.

According to Kirchhoff's current law, the current (I ₁ ) flowing through the first resistor (R10) is the same as the current (I ₂ ) flowing through the second resistor (R20).

  The above formula (1) can be summarized with respect to the reference voltage (Vref) as follows.

  The temperature coefficient of the reference voltage (Vref) generated from the reference voltage generator can be expressed as follows.

  Here, Tb> Ta.

  Referring to Equation (3), the temperature coefficient of the reference voltage (Vref) is the ratio between the temperature coefficient of the first voltage (V1) and the first resistance (R10) and the second resistance (R20) value. Determined by. The temperature coefficient of the first voltage (V1) output from the temperature proportional unit 84 is a determined value. For example, the temperature coefficient of the first voltage (V1) is determined to be + 0.2% / ° C. Accordingly, the temperature coefficient of the reference voltage (Vref) is determined to be a ratio of R20 / R10. For example, if the ratio of R20 / R10 is 2.5, the temperature coefficient of the reference voltage (Vref) is −0.5% / ° C.

  FIG. 4 is a graph showing temperature characteristics of the first voltage and the second voltage shown in FIG. The temperature coefficient of the first voltage (V1) is + 0.2% / ° C.

  FIG. 5 is a graph showing temperature characteristics of the reference voltage shown in FIG. The temperature coefficient of the reference voltage (Vref) is −0.5% / ° C.

  FIG. 6 is a specific circuit diagram according to an embodiment of the reference voltage generator shown in FIG.

Referring to FIG. 6, the reference voltage generating unit includes a current mirror circuit 86, a temperature proportional unit 84, and a voltage generating unit 85 independent of temperature. The current mirror circuit 86 includes a first PMOS transistor (PM1), a first NMOS transistor (NM1), and a third resistor (R30) connected in series between the power supply voltage (V _DD ) and the ground voltage. ) And. The current mirror circuit 86 further includes a second PMOS transistor (PM2) and a second NMOS transistor (NM2) connected in series between the power supply voltage (V _DD ) and the ground voltage. The gate of the first PMOS transistor (PM1) is connected to the gate of the second PMOS transistor (PM2). Similarly, the gate of the first NMOS transistor (NM1) is connected to the gate of the second NMOS transistor (NM2). The drain of the first PMOS transistor (PM1) is connected to the gate of the first PMOS transistor (PM1), and the drain of the second NMOS transistor (NM2) is connected to the gate of the second NMOS transistor (NM2). Is done. The ratio of the region of the first NMOS transistor (NM1) to the region of the second NMOS transistor (NM2) is P.

  The current mirror circuit 86 further includes a third PMOS transistor (PM3) and a fourth PMOS transistor (PM4) connected in parallel with the first and second PMOS transistors (PM1, PM2). The gates of the third and fourth PMOS transistors (PM3, PM4) are connected to the gate of the second PMOS transistor (PM2).

  The temperature proportional unit 84 is connected between the third PMOS transistor (PM3) and the ground voltage, and the temperature-independent voltage generation unit 85 is connected between the fourth PMOS transistor (PM4) and the ground voltage. Connected. The temperature proportional unit 84 includes a fourth resistor (R40) and a fifth resistor (R50) connected in series between the third PMOS transistor (PM3) and the ground voltage. The fuse (f1) is connected in parallel with the fifth resistor (R50). The temperature-independent voltage generator 85 includes a sixth resistor (R60) and a third NMOS transistor (NM3) connected in series between the fourth PMOS transistor (PM4) and the ground voltage. . The gate of the third NMOS transistor (NM3) is connected to its own drain.

The current mirror circuit 86 supplies the same current (I _D ) to the temperature proportional unit 84 and the temperature-independent voltage generation unit 85. The second voltage (V2) generated from the temperature-independent voltage generator 85 is as follows.

Here, Vn is a voltage flowing through the third NMOS transistor (NM3), W is the width of the third NMOS transistor (NM3), and L is the length of the third NMOS transistor (NM3). .

Referring to Equation (4), the third NMOS transistor NM3 has a negative second voltage (V2) value depending on the temperature, and the resistor has a second voltage (V2) value depending on the temperature. Has a positive value. Accordingly, the temperature-independent voltage generator 85 generates a constant voltage regardless of the temperature.

  The temperature proportional unit 84 generates a first voltage (V1) as shown in the following equation.

  According to equation (5) described above, the first voltage (V1) is dependent on the resistance value provided by the fuse (f1). The fuse (f1) can be made by laser fusing. The fuse (f1) can be used after being programmed into a logic instruction and stored in a nonvolatile memory. However, the fuse (f1) is only an example of a resistance variable means, and other resistance variable means may be used instead of the fuse (f1). For example, a transistor controlled by logic means may be used.

  If the resistance variable means is used, the first voltage (V1) is varied by the variable resistance value of the resistance variable means. The first voltage (V1) can be adjusted to be the same as the second voltage (V2) at a desired temperature by the variable resistance means. For example, the desired temperature is room temperature or 25 ° C.

  If the first voltage (V1) and the second voltage (V2) are set to be the same at a desired temperature, the same reference voltage (Vref) is obtained at the desired temperature regardless of the temperature coefficient of the reference voltage (Vref). Can occur. This is illustrated in FIG.

  FIG. 8 is a specific circuit diagram of another embodiment of the reference voltage generator shown in FIG.

  Referring to FIG. 8, the reference voltage generator includes a current mirror circuit 86, a temperature proportional unit 84, and a voltage generator 85 that is independent of temperature. The reference voltage generator of FIG. 8 excludes that the third NMOS transistor (NM3) is replaced with the first bipolar transistor (TB) in the voltage generator 85 independent of the temperature shown in FIG. This is the same as the reference voltage generator in FIG. The base of the first bipolar transistor (TB) is connected to the collector of the first bipolar transistor (TB). The operation of the reference voltage generation unit in FIG. 8 is the same as the operation of the reference voltage generation unit in FIG.

  FIG. 9 is a block diagram showing a liquid crystal display device to which the reference voltage generator according to the present invention is applied.

  Referring to FIG. 9, the voltage generator 10 includes a reference voltage generator 12 and a drive voltage generator 14. The drive voltage generator 14 generates a gate drive voltage to be applied to the gate driver circuit 16 using the reference voltage output from the reference voltage generator 12. Further, the voltage generator 10 generates a source drive voltage applied to the source driver circuit 18. The timing controller 20 generates a timing signal according to a video data signal applied from the outside, and outputs the timing signal to the gate driver circuit 16 and the source driver circuit 18. The gate driver circuit 16 and the source driver circuit 18 generate a gate driving signal and a source driving signal to be applied to the liquid crystal panel 22 in response to the timing signal and the driving voltage.

  The reference voltage generator 12 of the liquid crystal display device of FIG. 9 applies the reference voltage generator according to an embodiment of the present invention. FIG. 10 is a graph showing the temperature characteristics of the gate voltage in the liquid crystal display device shown in FIG. Referring to FIG. 10, the gate driving voltage has an inversely proportional characteristic as the temperature increases.

  As described above, the optimal embodiment has been disclosed in the drawings and specification. The terminology used herein is used only for the purpose of describing the present invention and is used to limit the scope of the invention as defined in the meaning and claims. It is not that. Further, those skilled in the art can understand that various modifications and equivalent other specific forms can be implemented without changing the technical idea and essential features of the present invention. Therefore, the true technical protection scope of the present invention should be determined by the technical idea of the claims.

It is a circuit diagram which shows a general reference voltage generation part. 2 is a graph illustrating reference voltages according to temperatures having different temperature coefficients in the reference voltage generation unit illustrated in FIG. 1. FIG. 3 is a circuit diagram illustrating a reference voltage generator according to an embodiment of the present invention. It is a graph which shows the temperature characteristic of the 1st voltage shown by FIG. 3, and a 2nd voltage. 4 is a graph showing temperature characteristics of a reference voltage shown in FIG. 3. FIG. 4 is a specific circuit diagram according to an embodiment of a reference voltage generator illustrated in FIG. 3. 5 is a graph illustrating reference voltages according to temperatures having different temperature coefficients in a reference voltage generation unit according to an embodiment of the present invention. FIG. 4 is a specific circuit diagram according to another embodiment of the reference voltage generator shown in FIG. 3. It is a block diagram which shows the display driver circuit to which the reference voltage generation part according to this invention is applied. 10 is a graph showing temperature characteristics of gate voltage in the display driver circuit shown in FIG. 9.

Explanation of symbols

82: Buffer amplifier 83: Voltage subtractor 84: Temperature proportional unit 85: Voltage generation unit 86: Current mirror circuit

Claims (33)

Including a reference voltage generating circuit for generating a reference voltage that is variable according to temperature;
The reference voltage generating circuit is selectively varied according to a temperature value at which a temperature coefficient of the reference voltage is selected, and the reference voltage has the same voltage level regardless of the temperature coefficient. Generation part.   The reference voltage generation unit according to claim 1, wherein the reference voltage generation circuit generates the reference voltage in response to a first voltage and a second voltage.   The reference voltage generation unit according to claim 2, wherein the first voltage is a temperature-dependent voltage, and the second voltage is a constant voltage regardless of the temperature.   The reference voltage generator according to claim 3, wherein the first voltage is a voltage that varies in proportion to a temperature.   The reference voltage generation unit according to claim 3, wherein the reference voltage generation circuit subtracts the first voltage value by the second voltage value.   2. The reference voltage generation circuit, wherein the first voltage value and the second voltage value are selectively varied, respectively, and each of the varied voltage values varies the temperature coefficient of the reference voltage. 5. A reference voltage generating unit according to 5. The reference voltage generation circuit includes:
A first resistor to which the first voltage is input;
An operational amplifier including: a non-inverting input terminal to which the second voltage is input; an inverting input terminal to which an output from the first resistor is input; and an output terminal to output the reference voltage; A variable resistor connected between an inverting input terminal and an output terminal of the amplifier and configured to vary the temperature coefficient of the reference voltage;
The reference voltage generation unit according to claim 3, comprising: A first voltage generator for generating the first voltage; and a second voltage generator for generating the second voltage;
The reference voltage generator according to claim 3, further comprising:   The first voltage generator includes a second resistor and a third resistor connected in series, and a resistance variable unit connected in parallel with the third resistor. 8. A reference voltage generator according to 8.   The reference voltage generator according to claim 9, wherein the resistance variable unit is adjustable to generate a desired voltage value according to the temperature value selected by the first voltage generator.   The reference voltage generator according to claim 10, wherein the desired voltage value is the second voltage.   9. The reference voltage generating unit according to claim 8, wherein the second voltage generating unit includes a temperature inversely proportional unit connected in series with a temperature proportional unit.   13. The reference voltage generating unit according to claim 12, wherein the temperature proportional means is a resistor, and the temperature inverse proportional means is a transistor.   The reference voltage generation unit according to claim 1, wherein the reference voltage generation circuit generates the reference voltage that decreases as the temperature increases. A first voltage generator for generating a first voltage;
A second voltage generator for generating a second voltage; and a voltage subtractor for generating a reference voltage obtained by subtracting the first voltage from the second voltage;
A reference voltage generator.   16. The voltage subtracting unit according to claim 15, wherein the first and second voltage values are selectively varied, and the varied voltage values vary the temperature coefficient of the reference voltage. Reference voltage generator described in 1.   The reference according to claim 16, wherein the first voltage generator generates a temperature-dependent voltage, and the second voltage generator generates a constant voltage regardless of the temperature. Voltage generator. The first voltage generator generates the first voltage having the same voltage value as the second voltage at a desired temperature,
The reference voltage generating unit according to claim 17, wherein the voltage subtracting unit generates the same reference voltage regardless of the temperature coefficient of the reference voltage at the desired temperature.   The reference voltage generator according to claim 15, wherein the voltage subtractor generates the reference voltage that decreases as the temperature increases.   A method of generating a reference voltage, comprising: generating a reference voltage having the same voltage value regardless of a temperature coefficient of the reference voltage at a selected temperature value.   The method of claim 20, wherein the generating step generates the reference voltage in response to the first voltage and the second voltage.   The reference voltage generation method according to claim 21, wherein the first voltage is a temperature-dependent voltage, and the second voltage is a constant voltage regardless of the temperature.   The method of claim 22, wherein the first voltage is proportional to temperature. The generation stage includes
Applying the first voltage and the second voltage;
Subtracting the applied first voltage from the applied second voltage;
The reference voltage generating method according to claim 22, further comprising: The generation stage includes
25. The reference voltage generation of claim 24, further comprising the step of selectively varying the temperature coefficient of the reference voltage according to changes in the applied first and second voltage values. Method. Generating the first voltage according to a resistance value; and generating the second voltage;
The reference voltage generation method according to claim 25, further comprising:   27. The method of claim 26, wherein the first voltage generating step includes adjusting the resistance value so that the first voltage becomes a desired voltage value at the selected temperature value. Reference voltage generation method. The reference voltage generation method according to claim 27, wherein the desired voltage value is the second voltage. Generating the second voltage; and generating the first voltage having the same voltage value as the second voltage at the desired temperature;
21. The reference voltage generation method according to claim 20, further comprising:   21. The method of claim 20, wherein the generating step generates the reference voltage that decreases as the temperature increases. A reference voltage generator, which generates the reference voltage having a constant voltage value regardless of the temperature coefficient of the reference voltage at the selected temperature even if the temperature changes, and responds to the reference voltage Generating a source driver voltage by generating at least one gate driver voltage;
A source driver generating a source driving signal in a display panel in response to the source driver voltage; and a gate driver generating a gate driving signal in the display panel in response to the gate driver voltage;
A display driver circuit comprising:   The reference voltage generator generates the reference voltage that decreases as the temperature increases, and generates a gate driving signal that decreases as the temperature increases in response to the reference voltage. Item 32. The display driver circuit according to Item 31.   The display driver circuit according to claim 32, wherein the display panel is a liquid crystal display panel.

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